Party-line automatic telephone system



Sept. 3, 1929. R. G. RXCHARDSON ET AL 1,727,133

PARTY LINE AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 23, 1923 3 Sheets-Sheet 1 Sept. 3, 1929- R. G. RICHARDSON ET AL 1,727,133

PARTY LINE AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 23, 1923 3 Sheets-Sheet 2 sun- John I EEZZam Emil-Leg E. B15115 p 1929- R. G. RICHARDSON ET AL 1,727,133

PARTY LINE AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 23, 1925 I 3 Sheets-Sheet 5 Inuau U15 Bud 1155i E.H1 char5mn-Juhn lEEHamH I Fatented Sept. 3, 1929.

iihll'll STATES l,7Z7,l33

PATENT QFFICE.

RGIDNEY G. RICHARDSUN, OF CHICAGO, AND JOHN I. BELLAMY, OF BROOKFIELD, ILLINOIS, ASSIGNOES, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC INC., OF. CHICAGO, ILLINOTS, A CGRPORATION OF DELAWARE.

PARTY-LINE AUTOMATIC TELEPHONE SYSTEM.

Application filed. February 23, 1923, Serial No. 620,603. Renewed February 9, 1929.

he present invention relates to selective ringing party line telephone systems in general, but is concerned more particularly with systems of the above character in which the source of ringing current for signalling a called subscriber is determined by a terminal per station, reference being ad to U. S. Patent No. 1,526,081, Owen, et al., issued Feb. 10, 1925, and the broad object, b iefly stated, is the production of new and improved circuit arrangements whereby the amount of equipment used in a system of this nature to select the ringing current is reduced to a minimum.

Other objects will be met with and explained from time to time duringthe course of the specification.

in order to carry out the main object of the invontiomthe ringing of calledstations is divided into as many periods as there are stations on a line, and ringing current of the proper sort to signal one station only, is

placed on the common ringing circuit during each period. Then, to call the desired station on aparty line, it is necessary only to connect the common ringing circuit to the line during the proper period. This is accomplished by a ringing relay in the connector circuit which is connected toone of a plurality of pick-up conductors, depending upon the station being called. This ringing relay, upon energizing over one of the pickup conductors, which it does when the source of ringing current corresponding to the pickup conductor in use is connected to the common ringing circuit, connects the common ringing circuit'to the called line and maintains the connection until the end of that ringing period is reached. The ringing relay operates the same way each time that ranging period recurs. I A The accompanying drawings, comprising Figs. 13, inclusive, show by means of the usual circuit diagrams a sutficient amount of apparatus in a system embodying the principles of the invention to enable the inventlon to be explained and understood. 1 7

ln order for Figsfl and 2 to be understood best, they should be arranged in order with the corrcspondinglines at the ends thereof in alignment, and in order for the modification shown in Fig. 3 to be understood, Fig. 3 should be substituted for Fig. 2.

Figure 1 shows the substation A of which lays.

the line terminates at the exchange in the line I switch C, and the selector E which is accessible to the line switch C. This drawing shows also the second selector E (denoted by Figure 3 shows the connector H which is similar to the connector H. The connector H is for use in a four-party semi-selective party line system. This drawing shows also the interrupter I and associated equipment which is used in the semi-selective system in conncction with the connector H and the other similar connectors.

Referring now particularly to Fig. 2, the invention will be described generally with reference thereto. The line of substation A terminates as usual at the line side of the main distributing frame M. D. F and is connected by the two-wire jumper 163 to the protector side of the M. D. F. The protector side of the D. F. is connected by switchboard cables to the line switch side of the intermediate distributing frame I. D. F. The three conductors for the line switch are taken off the line switch side of the I. D. F., as shown. Since the line of substation A is a party line, the associated contacts on the line switch side of the I. D. F. are not jumpered directly to the connector bank side of the I. D. F., but are connected by means of the jumper 162 to a so-called idler block, one of these being used for each four-party line.

The idler block shown has five sets of terminals. One of these sets of terminals is used up by the jumper 162, leaving the other four for jumpers, such as 161, between the idler block and the connector bank side of the I. D. F. The idler block shown, it may be stated, is representative of the others.

The contacts of the connector banks are cabled over to the connector bank side of the I. I). F. and are there connected up in order. Each set of connector bank contacts represents a station which may be a station on an individual line or a station on a party line, depending upon to where the associated jumper, such as the jumper 161, is connected. Any four sets of terminals, in the same group or in different groups of connectors, may be assigned to any party line. For instance, in the drawing the cycle station on the party line shown has been assigned the set of terminals 153 to 156, and the other station, cycle, 33 cycle, etc, may have assigned to them any of the 99 other sets accessible to the same connector or sets accessible to other groups of connectors, by merely running the proper jumpers.

'VVhen a party line station is signalled, it is necessary that the signalling be done in such a manner that the other stations on the line are not signalled. In this particular case, it has been chosen to use the so-called harmonic system of ringing. The four generators which supply the harmonic ringing current are shown diagrammatically in the lower left-hand corner of the drawing, and they furnish ringing current of the proper frequencies to selectively operate the tuned ringers on the party lines.

In order to choose between the four sources of ringing current when any particular station is called, a pick-up or ringing relay, such as relay 105 of the connector II, is provided for each connector. This relay is controlled in accordance with the cross connection of the bank contacts engaged by the ringing current wiper 151 of the connector II, and when energized, connects the common ringing lead 170 to the called line at the same time that the desired frequency of ringing current is placed on the common ringing lead by one of the ringing interrupter relays 176179, inelusive.

The contacts in the bank of wiper 151, of which one is provided for each station called by way of the connector II, are cabled to the left-hand side of the I. D. F. along with the line and test contacts as shown. Since there are four connector bank contacts in each set, the jumpers, such as 161, are fourconductor jumpers and the fourth conductor of each connects with one of the four pick-up conductors 17117t, inclusive, which are connected to the idler blocks, as shown. The correct pick-up conductor is, therefore, connected back to the ringing current terminal of each station, and provides for controlling the ringing relays, such as relay 105 of the connector II, in such a manner that the common ringing lead 170 is connected up to a called line during the time when it is carrying the desired one of the four frequencies of ringing current, the time at which lead 170 is connected up to a called line depending, in any one case, upon to which of the four sets of terminals on the idler block the terminals of the selected station are connected.

It will be noted that the thirty-three cycle pick-up conductor 17 2 is connected with the bottom terminal of the set 120 on the I. D. F. This is done on all such terminal sets, and while it is not used when the associated line is .a party line, it is used, as in Fig. 1, for the line of substation A, to take care of signalling a subscriber on an individual line by means of the thirty-three cycle generator which is generally used for individual line ringers on account of the fact that such ringers are not tuned and are ordinarily of such a type that they respond most readily to ringing current having a frequency of about thirty-three cycles.

The substations, such as A-A inclusive, are of the usual automatic type and have, in addition to the other well-known instrumentalities, calling devices for controlling the automatic switches.

The individual line switches, of which the line switch C is typical, are mechanically of the rotary type of which the wipers have no normal position and move in a forward direction only. The selector and connector switches such as the selectors E and E and the connectors H and H are mechanically of the well-known vertical and rotary type of switch and, accordingly, their bank contacts are arranged in horizontal rows or levels.

The interrupters I and I may have any desired mechanical construction and, as shown, each has an armor wiper which is adapted to operate continuously over its field of contacts.

In order to explain the operation of the system, it will be assumed that the subscriber at substation A desires to converse with the party line subscriber at substation A. In order to do this, the subscriber at substation A removes his receiver and then dials the directory number of the desired subscriber.

When the receiver is removed at substation A, line relay 14 energizes over line conductors 11 and 12. Upon energizing, line relay 14 places ground on private normal conductor 30 at armature 20, thereby making the calling line busy, and closing a circuit for switching relay 13 and stepping magnet 15 in series. As a further result of the energization of line relay 14L, it connects test wiper 22 to the junction of switching relay 13 and stepping magnet 15 at armature 19.

In case the trunk upon which the wipers of the line switch are standing is idle, switching relay 13 energizes immediately. Assuming the trunk to be busy, however, switching relay 13 is short-circuited by ground encountered -on the busy test contact by test wiper 22 and does not energize, and the wipers are rotated step by step by the buzzer-like action of stepping magnet 15, which operates through test wiper 22. When an idle trunk is reached, which trunk it will be assumed is the one terminating in bank contacts 24 26, inclusive, switching relay 13, being no longer short-circuited, energizes in series with stepping magnet 15. Stepping magnet 15, however, does not energize at this time on account of the high resistance of switching relay 13. Switching relay 13, upon energizing, opens a point in the test circuit and prepares the holding circuit at armature 17, and at armatures 16 and 18 disconnects line conductors 11 and 12 from the winding of line relay 14 and ground, and extends them by way of wipers 21 and 23, bank contacts 24 and 26, conductors 27 and 29, and armatures 58 and 61 and their resting contacts tothe upper and lower windings of line relay 41 of the selector E.

Line relay 41 now energizes over the calling subscribers loop and closes at armature 52 a circuit for release relay 42. Upon energizing, release relay 42 opens a point in the circuit of release magnet 46 and prepares a circuit for vertical magnet 47 at armature 54, and at armature 53 places ground on release trunk conductor 28, thereby closing the usual holding circuit for switching relay 13 of the line switch C before the slow-acting line relay 14 has had time to deenergize.

When the calling subscriber operates his calling device in accordance with the first digit in the desired number, the circuit of line relay 41 is opened a corresponding number of times. Each time line relay 41 deenergizes in response to one of the interruptions thereby produced, it closes a circuit for vertical magnet 47 as follows: from ground by way of the resting contact of armature 60 and said armature, armature 52 and its resting contact, armature 54 and its working contact, relay 43, and vertical magnet 47 to battery. By the operation of vertical magnet 47, the wipers 62-64, inclusive, are raised opposite the desired level of bank contacts. Relay 43 is energized in series with vertical magnet 47 and, being slow-acting, retains its armature attracted throughout the vertical movement. As a result of the energization of relay 43, it closes a circuit at armature 55 for stepping relay 44 by way of 01f normal contacts 51, which close upon the first vertical step, and interrupter contacts 50. Stepping relay 44, upon energizing, closes a locking circuit for itself at armature 56, and at armature 57 prepares a circuit for rotary magnet 48.

At the end of the vertical movement, slowacting relay 43 deenergizes and completes the circuit of rotary magnet 48 at armature 55. Rotary magnet 48, upon energizing, advances the wipers 62-64, inclusive, into engagement with the first set of bank contacts in the selected level, and, near the end of its stroke, opens the circuit of stepping relay 44 at interrupter contacts 50. Stepping relay 44, upon deenergizing, opens the circuit of to 'tary magnet 48 at armature 57, whereupon wiper 63, and stepping relay 44 energizes I from this same ground potential and closes the circuit of rotary magnet 48 again, whereupon the switch wipers are rotated into ongagement with the next set of bank contacts. This alternate operation of stepping relay 44 and rotary magnet 48 continues until an idle trunk is reached, which trunk it will be assumed is the one terminating in bank contacts -67, inclusive, whereupon switching relay 45, being no longer short-circuited, energizes in series with stepping relay 44. Stepping relay 44, however, does not energize at this time on account of the high resistance of switching relay 45. I upon energizing, opens a point in the test circuit and prepares the holding circuit at armature 59; disconnects ground from armature 52 of line relay 41 at armature 60, thereby opening the circuit of release relay 42; and at armatures 58 and 61 disconnects conductors 27 and 29 from the windings of line relay 41, and extends them by way of wipers 62 and 64, bank contacts 65 and 67, and the associated line conductors to the windings of the line relay of the selector E. The line and release relays (not shown) of the selector E now energize and prepares the switch for operation.

When the calling subscriber operates his calling device in accordance with the second digit in the desired number, the selector E raisesits wipers opposite the desired level or bank contacts and then selects an idle trunk. It will be assumed that the trunk selected at this time is the one extending to the connector H. That being the case, line relay 101 of the connector H energizes over the calling line and closes a circuit for release relay 103 at armature 128. Release relay 103, upon energizing, makes the usual circuit preparations at armatures 130 and 131, and at armature 129 places ground on release trunk conductor 7 5, thereby closing the usual holding circuit for the preceding switches C, E, and E.

WVhen the calling subscriber operates his calling device in accordance with the third digit in the desired number, a corresponding number of interruptions are produced in the circuit of line relay 101. In response to each of the resulting deenergizations of line relay 101, an impulse of current is sent to vertical magnet 111, the first impulse of current being sent over the following circuit: from ground by way of armature 128 and its resting con- Switching relay 45,

tact, armature 181 and its working contact, contact of off normal spring 114 and said spring, series relay 104-, and vertical magnet 111 to battery. By the operation of vertical magnet 111, the switch wipers 149152, inclusive, are raised step by step until they stand opposite the desired level of bank contacts. Relay 104 is energized in series with vertical magnet 111 on the first impulse of current and, being slow-acting, retains its armature attracted throughout the vertical movement. By attracting its armature 132, relay 104 serves to maintain its own circuit and that of vertical magnet 111 intact after the off normal springs have shifted, as they do upon the first vertical step. At the end of the vertical movement, relay 104 deei'iergizes and trans fers the operating circuit from the vertical to the rotary magnet.

WVhen the calling subscriber operates his calling device in accordance with the next and last digit of the desired number, the line relay 101 is deenergized a corresponding number of times. Upon each deenergization of line relay 101, an impulse of current is sent to rotary magnet 112, the first impulse of current being sent over the following circuit: from ground by way of armature 128 and its resting contact, armature 131 and its Working contact, normally open contacts controlled by ofi normal spring 114, armature 132 and its resting contact, resting contact of armature 139 and said armature, armature 146 and its resting contact, and rotary magnet 112 to bat tery. By the operation of rotary magnet 112, the wipers 149452, inclusive, are rotated step by step into engagement with the contacts 158-156, inclusive, of the called line. Relay 108 is energized in multiple with rotary magnet 112 upon the first impulse of current being delivered to the latter and, being slow-acting, retains its armature attracted throughout the rotary movement. Upon energizing, relay 108 disconnects test Wiper 150 from the upper winding of switching relay 109 and connects it to busy relay at armature 141, and at armature 142 places a shunt around armature 189 of busy relay 107 and its resting contact so as to guard its own circuit and that of rotary magnet 112 from being opened prematurely by busy relay 107, in case that relay energizes during the rotary movement, due to test wiper 150 passing over busy test contacts.

Assuming the called line to be busy, busy relay 107 is energized through test wiper 150 from ground on contact 154 when the switch wipers stop on the chosen contacts, and slowacting relay 108, upon deenergizing after the last impulse of current is delivered, disconnects itself and rotary magnet 112 from the operating circuit at armature 142, and at the normally closed contacts controlled by armature 141 completes a locking circuit for busy relay 107, which includes the working contact of armature and said armature and armature 138 and its working contact. Since, busy relay 107 is maintained energized, the lead from the busy signalling machine is connected up to the lower heavy talking conductor at armature 140 and, accordingly, a busy tone is sent back to the calling subscriber to inform him that he cannot obtain the de sired connection for the time being. Upon hearing this busy tone, the calling subscriber is expected to replace his receiver, whereupon the connection is released in a manner similar to that to be described hereinafter.

Assuming now that the called line is idle when called as hereinbet'ore described, there is no ground potential on test contact 154 and busy relay 107 is, therefore, not energized when the switch wipers come to rest upon the contacts associated with the called station. Under these conditions, slow-acting relay 108, upon deenergizing, completes a circuit for the upper winding of switching relay 109 in series with the combined switching and cutoff relay of the called line switch (not shown). The part of this circuit that is shown is as follows: from ground by way of the working contact of armature 130 and said armature, armature 138 and its resting contact, upper winding of switching relay 109, resting contact of armature 141 and said armature, test wiper 150, test contact 154, a conductor of jumper 161, a conductor of jumper 162, and thence by way of the private normal conductor 164 to battery by way of the cut-off relay of the line switch associated with the called line. The line switch associated with the called line as has been explained hereinbefore, is similar to the line switch C. Accordingly, the cut-oft relay corresponds to cut-ofi' relay 13 of the line switch C and is energized in series with the associated stepping magnet, similar to the stepping maget 15 of the line switch C. Due to the usual mechanical interlocking device between the armature of the cut-off relay of the called line switch and the armature of the associated line relay, the cut-off relay is energiezd only half way and, as a result, the wipers of the called line switch are not connected up.

In the connector H, switching relay 109, upon energizing over the above traced circuit, closes a locking circuit for itself at armature 145; applies direct ground to test wiper at armature 144; disconnects rotary magnet 112 and slow-acting relay 108 from the operating circuit at armature 146; connects up the line wipers at armatures 143 and 148; and at arn'iature 147 connects up ringing relay 105 to wiper 151 by way of armature 136 and its resting contact.

As shown in the drawing, the ringer at substation A is a fittycycle ringer, and the jumper 161 is connected to the fifty-cycle set of contacts on the idler block associated with the called line. That being the case, the cone stantly rotating arm 17 5 of the interrupter I rotates around, operating the ringing control relays 176-17 9, inclusive, one after another in order without producing any particular result as far as the called station is concerned until said arm 175 comes into engagement with the segment or contact associated with the ringing control relay 178. Relay 178, upon energizing, places the fifty cycle generator in connection with the common ringing lead at its left-hand armature, and at its right-hand armature grounds the fifty-cycle pick-up conductor 173, thereby closing for the first time a circuit for ringing relay 105 in the connector H as follows: from ground by way of the common fifty-cycle pick-up conductor 173, corresponding conductor in the jumper 161, bank contact 155, wiper 151, working contact of armature 147 and said armature, resting contact of armature 136 and said armature, and ringing relay 105 to battery. Upon energizing, ringing relay 105 connects the common ringing lead 170 with the lower line wiper 152 at armature \Vhen this occurs, current from the fifty-cycle generator is projected out over the called line and returns by way of the upper line wiper and the upper winding of ring-cutolf relay 106 to battery. The fifty-cycle ringer at substation A is operated bythis ringing current. The other ringers on the called line, being adjusted for diiferent frequencies of current, are not operated at this time.

When arm 17 5 of the interrupter I passes out of engagement with the contact associated with ringing control relay 178, said relay 178 deenergizes; disconnects the fiftyey'cle ringing current from the common ringing lead 17 0 at its left-hand armature. and at its right-hand armature removes ground from the associated pick-up conductor 173, whereupon ringing relay 105 in the connec= tor H deenergizes with results that are ap parent.

The arm 175 continues to rotate without causing any particular operation as regards the connector H until relay 178 is again energized, at which time the fifty-cycle ringing current is projected out on the called line in the hereinbefore described manner.

When the subscriber at substation A responds to the ringing of his bell by removing his receiver, a direct current bridge is closed across the conductors of his line. thereby operating ring-cut-oft' relay 106 in theconnector H. Upon energizing, ring-cut-off relay 106 closes a locking circuit for itself at armature 135; disconnects ringing relay 105 at armature 136; and at armatures 134 and 137 disconnects the line wipers 149 and 152 from its own upper winding and ground and extends them to the windings of the battery feed impedance 102. The callin and called subscribers may now converse each other as desired, the talking circuit being outlined by the heavy conductors.

At the end of the ensuing conversation, the two subscribers replace their receivers. The replacing of the receiver at the called substation does not produce any particular result, except that battery merely stops flowing over the called line.

When the receiver is replaced at substation A, the circuit of line relay 101 is opened and relay 101 deenergizes. Upon armature 128 being retracted, the circuit of release relay 103 is opened and a circuit is prepared for release magnet 110. Upon deenergizing in response to the prolonged opening of its circu1t, slow-acting release relay 103 removes ground from armature 138 of relay 107 at armature 130; disconnects ground from release trunk conductor 75 at armature 129, where upon relays 106 and 109 deenergize; and at armature 131 completes a circuit for release magnet 110 by way of oil normal contacts 113. Upon the energization of release magnet 110, the wipers of the connector H are restored to normal position, and the circuit of release magnet 110 is opened at off normal contacts 113 by the switch shaft when the wipers reach their normal position.

As a result of the ground potential being removed from release trunk conductor 75, switching relay 13 of the line switch C, switching relay of the selector E, and the corresponding relay (not shown) of the selector E deenergize. The deenergization of switching relay 13 of the line switch C restores conditions in that switch to normal. The deenergization of switching relay 45 of the selector E results in a circuit being closed for release magnet 46 at armature and its resting contact. This circuit includes arma tures 52 and 54 and their resting contacts and off normal contacts 49. The wipers of the selector E are restored to normal position in the usual manner upon the energization of release magnet 46, and the circuit of release magnet 46 is again opened at off normal contacts 49 when the switch wipers reach their normal position. The selector E is restored to normal in a similar manner.

, From the foregoing, it will be seen that a station on a party line can be signalled by any desired frequency of ringing current and that the frequency of ringing current used is not at all associated with the number of the called station. It can be seen in connection with Fig. 2, that if the number of the substation A is to be assigned to a different station on account of the subscriber at substation A moving or for some other like reason, the station to which that number is assigned can be signalled by any one of the four desired frequencies of ringing current by merely placing the jumper 161 on the correct set of contacts of the idler block associated with the line in question;

Referring now particularly to Fig. 3, the modification of the scheme which is used a four-party semi-selective system will be explained. In this system, as is well-known, the ringers of the stations ona four-party line are connected from either side of the line to ground, thus allowing a semi-selection to be made by merely ringing on one side of the line or the other. In order to complete the selection, or, in other words, to signal the correct subscriber, one ring and two rings,

respectively, are assigned to the stations whose ringers are connected between the same side of the line and ground. This is designated in the drawings by the references 2-, 2+, etc., the numerals referring to the number of bells to which the subscriber is in structed to respond and the minus and plus signs referring to the side of the line to which the ringers are connected.

Owing to the fact that some of the stations are signalled by two bells, that is, one ring following immediately after the preceding ring, it has been found necessary to provide only a momentary pick-up at the beginning of each ringing period and to hold up the ringing relays by a locking conductor which remains grounded throughout each ringing period.

In order to. explain the operation a little more in detail, it will be assumed that the subscriber at substation A is being called; that the desired line is idle; and that the connector H is the one used. That being the case, the line of substation A is seized by the connector H in the usual manner upon the energization of switching relay 240. Among the other things done by the switching relay 2 10, it connects up the ringing relay 201 to the wiper 207 at armature 206. As soon, after this occurs, as pick-up conductor 252 is grounded in response to the arm of the interru pter 1 coming into engagement with its contact 218, an energizing circuit is closed for ringing relay 201 as follows: from ground by way of the arm of interrupter I, pick-up conductor 252', corresponding conductor of jumper 259, bank contact 208, wiper 207, working contact of armature 206 and said arn'iature, resting contact of armature 205 and said armature, and the lower winding of relay 201 to battery. Relay 201, upon energizing, prepares a locking circuit for its up per winding at armature 232, and at armatures 203 and 20 ishifts the connection of the line wipers from battery and ground locally to the two common ringing leads 215 and 216.

As the arm of the interrupter I continues to rotate in the direction indicated by the associated arrow, it comes into engagement with the ringing segment 219 before it moves out of engagement with the pick-up segment 218. When the segment 219 is grounded, relay 213 energizes and places ground on the common locking conductor 217 at its right hand armature, thereby closing a locking circuit for the upper winding of ringing relay 201 before the pick-up circuit is opened. Eventually, the arm of the interrupter 1' moves off the pick-up segment 218 and is entirely on the ringing segment 219, thereby removing ground from pick-up conductor 252 so as to prevent any ringingrela'ys from energizing thereover until the arm of the interrupter it reaches that pick-up position again.

As a further result of the above mentioned energization of relay 213, the common ringing lead 215 is disconnected from battery and is connected to the right hand winding of the transformer T, which is connected to battery also, and on which ringing current is superimposed by the generator GEN. through the medium of the left hand winding of the transformer T.- l/Vhen this occurs, the ringer at substation A and the other ringer at substation A which is connected from the top or negative talking conductor to ground, are operated in. the usual manner.

Eventually, the arm of the interrupter 1 comes into engagement with the locking seg ment 220, thereby placing a multipled ground on the locking conductor 217 so as to maintain the said locking conductor grounded after the deenergization of relay 213, which occurs subsequently. .After an interval, the arm of the interrupter 1 passes out of engagement with the segment 219 and is wholly in engagement with the locking segment 220. Vv'hen this occurs, relay 213 deenergizes; removes ground from the locking conductor 21? at its right hand armature, leaving the said conductor grounded by way of the locking segment 220 of theinterrupter 1; and at its left hand armature shifts the common rlnging conductor 215 back to direct battery again,

thereby terminating the first ring.

When the arm of the interrupter 1' comes into engagement with ringing segment 221, which is multipled with the ringing segment 219 as shown, the circuit of relay 213 is again closed, and the second ring is effected upon m r l O the ringing lead 215 being shifted to the right hand winding of the transformer T again. The locking conductor 21? is maintained grounded at the right hand armature of relay 213, while said relay 213 is energized.

' When the arm of the interrupter 1 passes off the segment 221 and comes into engagement with the dead segment 222, relay 213 deenergizes and terminates the second ring by disconnecting lead 215 from the right hand winding of the ringing current transformer at its left hand armature. Also, relay 213 disconnects ground from the locking conductor 217 at its right hand armature, thereby opening the locking circuit of relay 201, whereupon relay 201 deenergizes; opens a still further point in its locking circuit at armature 232 and at armatures 203 and 20 1 disconnects the line wipers of the connector from the ringing leads 215 and 216, and connects them to battery and ground locally. The dead segment 222 is placed between the segment 221 and the following pick-up segment, to give sufiicient time for relay 213 to deenergize and remove the ringing current from the lead 215 before the following pickup conductor 251 is grounded.

The arm of the interrupter I continues to rotate without producing any particular result so far as the connection in question is concerned, until the pick-up segment 218 associated with pick-up conductor 252 is again grounded. When this occurs, the above described ringing operations are repeated.

l/Vhen the subscriber at substation A responds to the ringing of his bell by removing his receiver, a direct current bridge is closed across the conductors of his line, whereupon the ring cut-E relay 209 of the connector H energizes; extends the line wipers to the battery feed impedance 210 at its upper and lower armatures; and at armature 205 disconnects the lower winding of relay 201 from the pick-up wiper 207. The calling and called subscribers may now converse with each other in the usual manner, and when the conversation is terminated, the release of the connection takes place in the manner described hereinbefore.

From the foregoing description it is seen that the subscriber at substation A is signalled by means of two rings following one after another by ringing current connected to the negative line conductor. The subscribcr at substation A is signalled by ringing current on the negative conductor also. The subscribed at this .substation, however, is instructed to respond to the one bell rings only, and the pickup conductor 251 is associated with his line so that he is signalled during the ringing period which follows immediately after the arm of the interrupter ll has passed over the dead contact 222, at which time relay 214 is energized. This relay 214 is energized during the entire period, and is not dropped back at the middle of the period, as is the relay 213, thereby giving one long ring instead of two short ones.

The other ringing periods are used to signal subscribers such as the subscribers at substations A and A whose ringers are connected between the positive side of the line and ground. This is done in exactly the same way as described, except that the ringing current comes from the middle winding of the transformer T and is projected over the lower or positive line conductor instead of the upper one.

Vhat is claimed is:

1. In a telephone system, a link circuit, a line having a plurality of stations thereon, means for associating said link circuit with said line, means continuously operating in successive cycles for associating ringing current with said link circuit, each cycle being divided into as many ringing periods as there are stations on said line, each of said periods corresponding to a particular one of said stations, and means for projecting said ringing current out on said line by way of said link circuit only during the ringing period corresponding to the desired station.

2. In a party line telephone system, a link circuit, a party line having a plurality of stations thereon, means for associating said link circuit with said party line, means continuously operating in successive cycles for associating ringing current with said link circuit, each cycle being divided into as many ringing periods as there are stations on said line, each of said periods corresponding to a particular one of said stations, a relay individual to said' link circuit, means for operating said relay only during the ringing period corresponding to the desired station, and means controlled by said relay for projecting said ringing current out on said line each time said relay is operated.

3. In a party line telephone system, a party line having a plurality of stations thereon and having a like number of branches at the exchange, each branch corresponding to a particular station, means for extending a connection to said line by way of one of said branches, a common ringing circuit, means operating in successive cycles for associating ringing current with said circuit, each cycle being divided into as many ringing periods as there are stations on said line, each of said periods corresponding to a particular one of said stations, and means controlled in accordance with the branch of said line in use and eftective when a connection is extended to said line for projecting said ringing current out on said line by way of said extended connection only during the ringing period corresponding to thedesired station.

4;. In a selective ringing party line telephone system, a party line, switching mechanism forextending a call to said line, a signalling conductor, a plurality of diiierent sources of ringing current equal in number to the number of stations on said line, means effective during the call for connecting said sources to said conductor in rotation, one after the other, and means included in said switching mechanism for connecting said conductor to the called line at the time the said .conductor is connected to the particular source which corresponds to the desired station on said line.

5. In a selective ringing party line telephone system, a party line, switching mechanism for extending a call to said line, a sig nailing conductor, a plurality of (lilierent sources of ringing current equal in number to the number of stations on said line, means eftective during the call for connecting said sources to said conductor in rotation, one

after the other, a ringing relay in said switching mechanism for connecting said conductor with the called party line, and ringing control circuits such that said relay is energized only when the particular source which said sources with said conductor in rotation,

one after the other, while said switch remains connected with said line, a ringing relay in said connector for connecting'said conductor with the called party line, and a ringing control circuit established by the operation of said connector for energizing said relay each time the particular source corresponding to the desired station is connected to said conductor.

7. In a selective ringing party line telephone system, a party line, an automatic connector switch and means for operating it to connect with said line, a signalling conductor, a plurality oi different sources of ringing current equal in number to the number of stations on said line, means for connecting said sources with said conductor in rotation, one after the other, while said switch remains connected with said line, a plurality of control conductors, one for each of said sources, means for grounding each control conductor when its associated source is connected to said signalling conductor, a ringing relay in said connector for connecting said signalling conductor to the called line, and a circuit for said relay including the particular control con- (luctor which is effective to energize said relay at the time the source which corresponds to the desired station is connected to said signalling conductor.

8. In a selective ringing party line telephone system, means for extending a connection to a called party line, a plurality of ringing control conductors one of which is selected when the connection is established, each control conductor corresponding to a diiil'ercnt station on said line, a signalling circuit, means for periodically altering said circuit to adapt the same for signalling the sta tions on said line in turn, and means controlled over the selected control conductor for connecting the signalling circuit to the called line only when its character is such that the desired station will be signalled.

9. In a selective ringing party line telephone system, a si nalling circuit, a relay for connecting said circuit to a called party line, and a ringing machine for periodically altering the character oi said circuit to adapt the same for signalling all the stations on said line in turn, said machine also coinprising means for energizing said relay only at the time the said circuit is of such a character that it will signal the wanted station.

10. In a selective ringing party line telephone system, a signalling circuit, a relay for connecting said circuit to a called party line, a plurality of generators, each corresponding to a diflerent station on said line, continuously operating means for connecting said generators in said circuit in rotation, one after the other, and means for energizing said relay only when the proper generator for signalling the desired station is connected.

11. In a selective ringing party line telephone system, a signalling circuit, a ringing relay for connecting said circuit to a called party line, a plurality of generators for signailing the different stations on said line, a corresponding number of interrupter relays for connecting said generators in said circuit successively, circuits controlled by said interrupter relays successively for energizing said ringing relay, a circular interrupter divided into as many sections as there are interrupter relays, and means for continuously operating said interrupter to energize said interrupting relays in rotation.

12. In a telephone system, a party line having a plurality of stationsthereon and terminating on. tour bank contacts, one of which is individual to a station on said line, a connector switch, means for operating said switch to connect with said bank contacts, a continuously rotating interrupter having as many ringing sectionsas there are stations on said line, a signalling circuit having as many diflerent kinds of ringing current sources associated therewith as there are stations on said line, a ringing relay in said switch, means responsive to the seizure of said line for connecting said relay to said individual contact, and means responsive to said interrupter rotating over the section corresponding to the seized individual contact for energizing said relay and for connecting said signalling circuit to the correct ringing current source to project the desired ringing current out on said line.

13. In a telephone system, a connector switch for calling a party line, a ringing relay in said switch, different sources of ringing current. corresponding, respectively, to the different stations on said party line,

means for automatically associating said sources with said relay in turn, and means for energizing said relay to apply the associated source to the party line only when such source corresponds to the desired station.

14:. In a telephone system, a party line connector switch, ringing means individual to said switch, a plurality of control conductors for said ringing means, means in said connector for selecting a control conductor at the same time the connector is operated to connect with a party line, aplurality of ringing current sources corresponding, respectively, to the stations on said party line, and ringing means common to said switch and other switches for successively associating said sources with said individual ringing means and for successively rendering said control conductors active.

15. In a telephone system, a connector switch, a ringing relay in said switch having contacts for connecting ringing current to a line called by said switch, sources of ringing current, and a device common to said connector and other connectors for successively connecting said sources to one of said contacts. I

16. In a connector switch for connecting with a called line, a ringing relay energized intermittently to apply ringing current to the called line, a self-locking ring cut-01f relay, and means controlled by said self-locking relay for disconnecting ringing current from the called line independent of said ringing relay.

l7. In a connector switch for connecting with a called line, a ringing relay for closing a ringing circuit to apply ringing current to the called line, a circuit for energizing said relay, a ring cut-oil relay included in the ringing circuit with the called line, a locking circuit for said ring cut-off relay, and contacts on said ring cut-oft relay for opening the ringing circuit and also for opening the circuit of said ringing relay.

18. In a telephone system, a connector switch having line wipers and a test wiper for connecting with and for testing a called line, said connector having another Wiper operated simultaneously with said line wipers, a ringing relay in said connector, and an energizing circuit for sa-idrelay including said other wiper.

19. In a telephone system, a connector switch having line wipers for connecting with a called line, said connector having another wiper operated simultaneously with said line wipers, a ringing relay in said connector, an energizing circuit for said relay including said other wiper, and ringing control equipment common to said connector and other connectors for closing said circuit.

20. In a telephone system, connector switches, party lines, branches of each party line accessible to said connectors, a control conductor associated with each branch, means for operating one of said connectors to connect with one of said lines via one of its branches, a ringing conductor common to said connectors, a plurality of sources of ringing current, means for connecting said sources to said ringing conductor successively and for connecting a source of potential to the control conductors of the branches of each of said party lines successively, and

means in the operated connector operative when said source of potential is connected to the control conductor associated with the branch in use for connecting the said ringing conductor to the connected called line.

21. In a telephone system, connector switches, party lines, branches of each party line accessible to said connectors, means for operating one of said connectors to connect with one of said lines via one of its branches, selective signalling means common to said connectors and to said lines, and means individual to the connector in use controlled by said common selective signalling means in accordance with the branch in use for selec tively signalling a particular station on the line.

- 22. In a telephone system, a connector having line wipers for connecting with a called line and another wiper operated simultaneously with said line wipers, a ringing relay in said connector, an energizing circuit for said relay including said other wiper, and means for intermittently opening and closing said circuit.

23. In a telephone system, a connector having line wipers for connecting with a called line and another wiper operated simultaneously with said line wipers, a ringing relay in said connector, an energizing circuit for said relay including said other wiper, and means common to said connector and other connectors for intermittently opening and closing said circuit.

24. In a telephone system, a party line, a source of ringing current, a relay and a set of terminals corresponding to a station on said line, a ringing circuit, means for operating said relay periodically to connect said source of ringing current to said ringing circuit and to connect a characteristic potential to a terminal of said set, and means controlled over said terminal for rendering said ringing circuit effective to signal the corresponding station on the line.

25. In a telephone system, party lines ter- 'minating on a plurality of sets of contacts, each of said sets corresponding to a station on a line, connectors, a ringing circuit com 'mon to said connectors to which ringing currents of different characteristics are successively connected in continuous cycles, a plurality of sets of line contacts accessible to said connectors, a connecting rack for variably connecting any one of said first sets 01 contacts with any one of said sets of line contacts, means for operating any one of said connectors into engagement with a random one of said sets of line contacts, and means in the connector controlled over the engaged set of line contacts for rendering said ringing circuit effective to signal a particular station on the line corresponding to the particular set of contacts connected to the engaged set of line contacts.

26. In a telephone system, groups of connectors, each group comprising a plurality of connectors, sets of line contacts foreach group accessible only to the connectors of a group, a ringing circuit common to connectors of all groups, a plurality of sources of ring ing current, means for successively connecting said sources to said ringing circuit in continuous cycles, a party line terminating on 10 a plurality of sets of contacts, each set corresponding to a station on the line, a connecting rack for variably connecting one of said second sets of contacts With any one of said sets of line contacts, means for operating a connector into engagement with the connected set of line contacts, and means in the connector controlled over the engaged set of line contacts for rendering said ringing circuit efiective to signal the particular station on the line corresponding to the set of contacts With which the engaged set of line contacts is connected.

Signed at Chicago, Illinois, this 15th 'day of February, 1923.

RODNEY Gr. RICHARDSON. Signed at Chicago, Illinois, this 15th day of February, 1923.

JOHN I. BELLA'MY. 

